Field of the Invention
The invention relates generally to shielding elements, and more particularly to an improved one-piece board level shielding element for electrical or electronic components of an electric or electronic circuit with a cover that can be removed for repair of the component by peeling away the top cover of the shield.
Related Art
Shielding elements are used in electric and/or electronic circuits to screen specific components of the circuit against electromagnetic radiation, in particular against spurious emission or irradiation. In particular, screening or shielding elements are used to comply with the requirements of EMC (electro magnetic compatibility) standards.
Usually such shielding elements have an annular side wall that can be mounted on a printed circuit board in a usual way, e.g. by soldering, and that surrounds the components to be shielded. After mounting the annular side wall and the components to be shielded onto the printed circuit board, a cover is used to close a ceiling opening that is defined by the upper edge of the annular side wall. A bottom opening that is defined by the lower edge of the side wall is closed by the substrate or printed circuit board. The terms “upper” and “lower” are used in this description to define the location of parts of the shielding element relative to the substrate irrespective of the orientation of the substrate itself. Hence, the upper edge of the side wall is that edge that is in a remote position whereas the lower edge is that edge that is in contact with the substrate after mounting.
As described above, mounting of a conventional shielding element onto a printed circuit board needs two mounting steps: First, mounting the side wall to the printed circuit bar and second, fixing the cover to the side wall. Often it is necessary to access the component for replacement or repair. A wide variety of methods to do this have been proposed. For example, U.S. Pat. No. 6,903,262 discloses a one-piece shielding element with notches in the planar shield cover to form a predetermined breaking line. The use of opposed V-shaped grooves is suggested in U.S. Pat. No. 6,831,224 for breakably and releasably opening the shield yet maintain a bendable hinge. U.S. Pat. No. 6,384,324 provides a shielding screen wherein the upper face has a precut line and holes to allow removal of the upper face of the shield. U.S. Pat. No. 5,614,694 provides shear lines and a hinge to allow the metallic cover to be raised and closed.
Costs are a driving force in the electronics industry. Typical board level shield having a two piece construction includes a shielding element composed of a shield cover or lid mounted on a side wall soldered to a circuit board surrounding the component. The side walls include holes or dimples for receiving corresponding projections or holes for engaging the walls of the lid. Such a two piece construction requires almost twice as the raw materials and processing costs of a one-piece design.
Notwithstanding these improvements in a variety of board level shields, there remains a need to provide yet an easy to install and less expensive way to provide access to the shielded electronic components that need to be serviced.